Question : 504 Helo command rejected: need fully-qualified hostname

I recently set up a SMTP server on our static IP. Before that our email used to be thru a hosting provider. Occasionally I get a returned email with an error "504 Helo command rejected: need fully-qualified hostname". This appears to bounce back from the recipient's mail system because our DNS record must not be configured quite right.

For example, our SMTP server's domain name is "mail.server.com". When I telnet to our SMTP server and enter the HELO command, it replies back with the first part of the domain name, which is "mail". The reason for the "504 Helo command rejected" is because the whole domain "mail.server.com" is expected as a reply--not just the "mail" response.

Question is...how do I fix this?  Is this a DNS configuration problem?

Answer : 504 Helo command rejected: need fully-qualified hostname

Your HELO *must* be an FQDN. RFC 2822 is fairly plain on this, and any sane MTA is going to refuse "mail" as a HELO. Mine do.

This is NOT a DNS problem. The problem is that your Kerio server is not conforming to standards. I don't know Kerio so I can't say if this is a problem with the software or merely a configuration issue, but in any event, it is NOT a DNS problem.